Laff

Laff is the health of Toons. The laff meter resembles a Toon's head and is shown at the bottom left corner of the interface. Toons start with 15 laff; the current maximum a Toon can have is 137. When a Toon hits zero laff, the Toon goes sad and is sent back to the nearest playground of a particular neighborhood. If the Toon goes sad in a street battle, the Cog that the Toon was battling is seen jumping around, teasing the Toon in a childish manner. After going sad, all the Toon's gags are taken away by the Cogs. While sad, a Toon's laff meter is a sickly lime green, and the Toon cannot exit the playground, board the Trolley, go fishing, board a golf cart, nor go to his or her friends.

During the Beta stage of Toontown Rewritten, there was a bug where Toons could go inside Toon Buildings while being sad, making teleportation work as normal.

Purposely making other Toons go sad in battle by either abandoning them, or letting the Cogs make them go sad, is known as "Greening". Greening Toons can result in receiving a punishment on their account.

in the final phase of all boss battles, a Toon's laff meter is displayed above their head while they have at least one laff point is missing. This feature made its first appearance during Doomsday from the Alpha stage of Toontown Rewritten.

There is a glitch where Toons start with 16 laff, but then reset to 15 laff upon restarting the game.

Yes, TTR has a full storyline to explain everything- even why people have to start over at 15 laff points. You'll see parts of it as development continues, but it is a pretty deep story that won't be fully revealed for a while. While the game is still going to be targeted at children, I want to add deeper aspects than "cogs are bad."